Paul Metsa was an eight-year-old growing up on the Iron Range when President John F. Kennedy was killed in November, 1963.

Metsa remembers sitting with his parents, riveted by the live TV coverage, as they watched authorities transfer suspected assassin Lee Harvey Oswald from the Dallas police station jail to a maximum security prison.

"And then boom, all of a sudden it happened," he recalled. "Jack Ruby appears and shoots Lee Harvey Oswald.

"It was the first time in my life, as a young white middle class American, where I really felt the presence of evil."

The 50th anniversary of the JFK assassination has provided an opportunity for Metsa, a Minnesota folk musician, to dust off one of his most haunting songs. He wrote "Jack Ruby" more than 21 years ago, but the questions at the heart of the tune still plague the nation.

In his late 20s, Metsa became consumed by the assassination. Like many, he questioned the findings of the Warren Commission established to investigate the president's death and its lone gunman theory. He read every conspiracy book he could find. As he began writing songs, he started to picture the most nefarious underworld figure associated with the assassination, Dallas nightclub owner Jack Ruby.

Metsa thought the name Jack Ruby had a poetic ring to it, like "John Henry," the steel driver who beat the machine in a race to build a railroad tunnel through a mountain and then died, or "John Hardy," the railroad worker who killed a man during a craps game and was hanged. Both are American folk standards.

"John Henry, John Hardy, Jack Ruby," he said. "You know, to me. psychically, it all kind of made sense."

In the early 90s, while living in a spooky Minneapolis mansion, Metsa came across an article about Jack Ruby's brother. He was selling all of Ruby's personal effects, including the Cavanagh hat he was wearing when he shot Oswald.

Jack RubyAP Photo

"At that point it just dropped down from the sky -- 'Jack Ruby, Jack Ruby, in a Cavanagh hat, whoever taught you to shoot a pistol like that, you snuck in the basement and you stood in the back, Jack Ruby, Jack Ruby in a Cavanagh hat' - and I had the chorus," Metsa said. "And boom I was off to the races."

But the song doesn't aim to make a folk hero out of Jack Ruby.

"Well, he's a bit of an anti-hero, really," he said. "The more you read about Jack Ruby, the deeper into the rabbit hole you get with the whole conspiracy."

Metsa's song traces Ruby's evolution from an Al Capone errand boy in Chicago to nightclub owner in Dallas, with ties to Cuba, the mob, and the police. With every biographical verse, the conspiratorial possibilities widen.

"He was such, I believe, a key player in tying together the rogue elements for the various facets of the conspiracy, I felt I could best build the song on his life story," he said.

Metsa has his own theory involving a wide-ranging conspiracy, but he's proud he left questions unanswered in "Jack Ruby."

"I didn't write it as a conspiracy researcher, although in a way I was," he said. "And I didn't write it as a private detective, although in a way that's what you turn out to be when you start to study it. I wrote it as a songwriter."

In "Jack Ruby," Metsa pleads for witnesses to come forward, for the truth to be revealed. But more than two decades after he wrote it, the mystery of the JFK assassination hasn't been resolved, at least not to the satisfaction of the American people. Metsa doesn't think we'll ever really know what happened.